Group-III nitride compound semiconductor device

ABSTRACT

An object of the present invention is to provide a large-size light-emitting device from which uniform light emission can be obtained. 
     That is, in the present invention, in a device having an outermost diameter of not smaller than 700 μm, a distance from an n electrode to a farthest point of a p electrode is selected to be not larger than 500 μm.

TECHNICAL FIELD

The present invention relates to a Group III nitride compoundsemiconductor device. The invention is adapted for improvement inelectrodes of a Group III nitride compound semiconductor light-emittingdevice such as a blue light-emitting diode.

BACKGROUND ART

In a Group III nitride compound semiconductor light-emitting device suchas a blue light-emitting diode, various proposals have been made forobtaining uniform light emission from the whole surface of the device.

For example, in Unexamined Japanese Patent Publication No. Hei. 8-340131and Unexamined Japanese Patent Publication No. Hei. 10-117017, a pauxiliary electrode is provided radially on an upper surface of a pcontact layer to attain uniformity of electric current density injectedinto the p contact layer. On the other hand, for example, as describedin Unexamined Japanese Patent Publication No. 10-275934, a translucentelectrode may be stuck on an upper surface of a p-type contact layer sothat a p seat electrode is provided thereon. In this example, a pauxiliary electrode is extended from the p seat electrode along sides ofthe device.

Unexamined Japanese Patent Publication No. Hei. 9-97922 and UnexaminedJapanese Patent Publication No. 2000-22210 have disclosed the case wherean n auxiliary electrode is provided along sides of the device from an nseat electrode formed in a corner portion of the device, by way ofexample.

Unexamined Japanese Patent Publication No. 2000-164930 has disclosed acomb-like electrode.

According to the present inventors' examination, it has been found thatit is preferable to increase the chip size of light-emitting diodes usedin a signal or the like in which high luminance is demanded andlight-emitting diodes of one color are collectively used. This isbecause if the number of light-emitting diodes used can be reduced byincrease in chip size, a circuit for evenly distributing an electriccurrent to respective light-emitting diodes can be designed easily andsimply as well as the number of steps for assembling the light-emittingdiodes can be reduced to attain reduction in production cost.

Therefore, the inventors have made examination again and again toincrease the chip size of light-emitting diodes. As a result, thefollowing problems have been found.

Since the resistance of an n contact layer (a layer on which an nelectrode is formed) in a light-emitting diode is relatively high, anelectric current cannot sufficiently go around to a portion far fromthen electrode so that light emission is reduced in the portion. On theother hand, intensive light emission is obtained in a portion near the nelectrode, so that light emission becomes uneven on the whole of thedevice. In a conventional small-size device (300 to 400 μm□) viewed fromthis point, the portion far from the n electrode was more or less dark,but was limited to a very small area so that the unevenness of lightemission was substantially not a large obstacle.

If the chip size becomes large, the amount of an electric currentapplied to the p seat electrode must be increased when preferablecurrent density injected per unit light-emitting area is to be kept. Thecurrent applied to the p seat electrode flows from the p seat electrodeinto the translucent electrode. If the amount of the current becomeslarge, there is a high possibility that burning (burning off thetranslucent electrode in a joint portion by generated Joule heat) mayoccur between the p seat electrode and the translucent electrode. Thearea of an interface between the p seat electrode and the translucentelectrode is a factor for deciding the amount of the current(permissible current quantity) permitted to be injected into the p seatelectrode. It is conceived that the permissible current quantity canincrease as the area increases.

If one p seat electrode and one n seat electrode are used in combinationwhen preferred current density is to be secured in an effectivelight-emitting surface of a large-size chip having an outermost diameterof not smaller than 700 μm, there is a fear that mold resin may beburned by heat generated in a bonding wire portion or the bonding wireitself may be broken by heat unfavorably.

DISCLOSURE OF THE INVENTION

The invention is provided to solve at least one of the aforementionedproblems. That is, in the present invention, there is provided a GroupIII nitride compound semiconductor device which is a device having anoutermost diameter of not smaller than 700 μm, wherein a distance froman n electrode to a farthest point of a p electrode is not larger than500 μm.

According to the Group III nitride compound semiconductor deviceconfigured as described above, the farthest point of the p electrodefrom the n electrode is with in the aforementioned distance. Hence, evenin the case where the resistance of an n-type semiconductor layer ishigh, electrons are sufficiently injected into the farthest deviceportion from the n electrode (electric current is diffused). As aresult, light is emitted more evenly from the whole surface of thedevice.

Incidentally, the current density and the luminous output of thelight-emitting device have such relation that the luminous output issaturated when the current density exceeds a predetermined value. Thatis, even in the case where current density exceeding the predeterminedvalue is injected, it is impossible to obtain increase in the luminousoutput in accordance with the current density. It is thereforepreferable that current density near the predetermined value is achievedon the whole region of the device in order to achieve both high luminousoutput and high luminous efficiency. When the distance between the nelectrode and the p electrode is defined as in the invention, thepreferred current density can be obtained on the whole region of thedevice and, accordingly, a device excellent in luminous efficiency canbe provided.

Incidentally, in this specification, the n electrode has an n seatelectrode, and an n auxiliary electrode extended from then seatelectrode whereas the p electrode has a p seat electrode, and a pauxiliary electrode extended from the p seat electrode. The outermostdiameter of the device is the length of the longest one of lines allowedto be drawn on the device in a plan view of the device. When the deviceis rectangular, the outermost diameter of the device is the length of adiagonal line. When the device is rhombic, the outermost diameter of thedevice is likewise the length of a diagonal line. When the device iscircular or elliptic, the outermost diameter of the device is the lengthof a line passing through the center of a circle or ellipse. Asdescribed above, the shape of the device is not particularly limited.Besides the aforementioned shapes, polygonal shapes such as a hexagonalshape, an octagonal shape, etc. may be used as the device shapes.

The upper limit of the distance between the n electrode and the pelectrode located farthest from the n electrode is selected to be morepreferably 400 μm, further more preferably 350 μm.

In the case of a rectangular chip, such configuration is preferablyapplied to a chip having a length of 500 μm or more on one side (700 μmor more in outermost diameter). In a conventional n electrodeconfiguration, if the chip size becomes large as described above, thereis fear that a portion which is darkened because it is too far from then electrode to obtain sufficient current density may form anunacceptably large region, and that the region may appear in the centralportion of the device to make the luminous form unsuitable. In the caseof a rectangular chip, the length of a side is selected to be morepreferably not smaller than 600 μm, further more preferably not smallerthan 700 μm, most preferably not smaller than 800 μm.

In an aspect of the invention, configuration that the n auxiliaryelectrode is extended from the n seat electrode to the central portionof the device is used so that the distance between any point of the pelectrode and the n electrode can be selected to be in the predeterminedrange.

Since the n auxiliary electrode is present in the central portion of thedevice, the distance from the n auxiliary electrode to any cornerportion of the device is kept constant. Hence, reduction in luminousoutput from the corner portions can be prevented.

When the n electrode has been improved in the aforementioned manner tosecure uniform diffusion of current to the n-type semiconductor layer,the next problem has loomed up newly.

Also in the type in which a translucent electrode is stuck on a p-typesemiconductor layer to attain diffusion of current, if the chip size ismade so large that the distance from the p seat electrode or from the pauxiliary electrode becomes large, the resistance of the translucentelectrode itself as a thin film cannot be ignored so that an electriccurrent cannot be sufficiently injected into a far portion of the p-typesemiconductor layer from the p seat electrode or from the p auxiliaryelectrode.

In an aspect of the invention, therefore, the distance from any point onthe translucent electrode to the p seat electrode or the p auxiliaryelectrode is selected to be in a range of from 0 to 1000 μm.

According to the Group III nitride compound semiconductor deviceconfigured thus, all points of the translucent electrode are within theaforementioned distance from the p seat electrode or from the pauxiliary electrode. Hence, an electric current can be sufficientlydiffused to the farthest portion of the translucent electrode from the pseat electrode or from the p auxiliary electrode so as to be injectedinto the p-type semiconductor layer just under the translucentelectrode. As a result, light can be emitted substantially evenly fromthe whole surface of the device. The upper limit of the distance betweenany point on the translucent electrode and either of the p seatelectrode and the p auxiliary electrode is selected to be morepreferably 500 μm, further more preferably 450 μm, further further morepreferably 400 μm, most preferably 350 μm.

In the case of a rectangular chip, such configuration is preferablyapplied to a chip having a length of 500 μm or more on one side (700 μmor more in outermost diameter). In a conventional p electrodeconfiguration, if the chip size becomes large as described above, thereis fear that a portion which is darkened because it is too far from thep electrode to obtain sufficient current density may form anunacceptably large region, and that the portion may appear in the centerof the device to make the luminous form unsuitable. In the case of arectangular chip, the length of a side is selected to be more preferablynot smaller than 600 μm, further more preferably not smaller than 700μm, most preferably not smaller than 800 μm.

In this manner, in an aspect of the invention, configuration in whichthe p auxiliary electrode is extended from the p seat electrode to thecentral portion of the translucent electrode is used so that thedistance from any point on the translucent electrode to the p seatelectrode or the p auxiliary electrode can be selected to be in thepredetermined range.

Since the p auxiliary electrode is present in the central portion of thetranslucent electrode, the distance from the p auxiliary electrode toany corner portion of the translucent electrode is kept constant. Hence,reduction in luminous output from the corner portions can be prevented.

In the Group III nitride compound semiconductor device having both the nelectrode and the p electrode configured as described above, it ispreferable that then auxiliary electrode and the p auxiliary electrodeare arranged like a comb in a plan view of the device. The device doesnot operate (the device does not emit light when the device is alight-emitting device) in certain portions of the n auxiliary electrodeand the p auxiliary electrode. Hence, when the n auxiliary electrode andthe p auxiliary electrode are arranged like a comb, the inoperativeportions can be disposed as symmetrical or regular patterns in thedevice, so that the device can be used easily. In the case of alight-emitting device, light can be taken out evenly.

In the Group III nitride compound semiconductor device having both the nelectrode and the p electrode configured as described above, it ispreferable that then auxiliary electrode and the p auxiliary electrodeinclude portions arranged in parallel with each other in a plan view ofthe device. The device does not operate (the device does not emit lightwhen the device is a light-emitting device) in certain portions of the nauxiliary electrode and the p auxiliary electrode. Hence, when theparallel portions are disposed, the inoperative portions can be disposedas symmetrical or regular patterns in the device, so that the device canbe used easily. In the case of a light-emitting device, light can betaken out evenly.

As the chip size increases, electric power consumed by the deviceincreases, and the current applied between the seat electrodesaccordingly increases. If one seat electrode is provided on each of pand n sides as in the conventional case, there may occur a problem thatthe mold resin is burned off by heat generated in the bonding wireportion or that the bonding wire itself is broken by the heat.Therefore, in another aspect of the invention, a plurality of p seatelectrodes and a plurality of n seat electrodes are provided. As aresult, the aforementioned problem is solved.

In the case of a rectangular chip, the preferred chip size for theprovision of the plurality of p seat electrodes and the plurality of nseat electrodes is such that the length of a side is not smaller than500 μm (the outermost diameter is not smaller than 700 μm). The lengthof a side is selected to be more preferably not smaller than 600 μm,further more preferably not smaller than 700 μm, most preferably notsmaller than 800 μm.

If the electric power consumed by the light-emitting device increasesbecause of increase in the chip size of the light-emitting device, therearises a problem of burning between the p seat electrode and thetranslucent electrode in addition to the aforementioned problem. It istherefore preferable that a p auxiliary electrode is provided to extendfrom the p seat electrode. When the p auxiliary electrode is provided, asufficient area can be obtained between the p seat electrode and thetranslucent electrode and between the p auxiliary electrode and thetranslucent electrode to thereby prevent occurrence of the burning.Hence, the amount of current (permissible current quantity) allowed tobe applied to the p seat electrode increases, so that the amount ofcurrent required for emitting light from the whole surface of the devicecan be kept sufficiently.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 explains the layer structure of a light-emitting device accordingto an embodiment of the invention;

FIG. 2 is a plan view showing an example of arrangement of electrodes inthe light-emitting device according to this embodiment;

FIG. 3 is a front view showing this example;

FIG. 4 is a back view showing this example;

FIG. 5 is a left (right) side view showing this example;

FIG. 6 is a bottom view showing this example;

FIG. 7 is a reference plan view showing a transparent portion(transparent electrode);

FIG. 8 is a partly cutaway enlarged sectional view taken long the lineA—A in FIG. 2;

FIG. 9 is a partly cutaway enlarged sectional view taken long the lineB—B in FIG. 2;

FIG. 10 is an enlarged sectional view taken long the line C—C in FIG. 2;

FIG. 11 is an enlarged sectional view taken long the line D—D in FIG. 2;

FIG. 12 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to another embodiment of theinvention;

FIG. 13 is a front view showing this example;

FIG. 14 is a back view showing this example;

FIG. 15 is a left (right) side view showing this example;

FIG. 16 is a bottom view showing this example;

FIG. 17 is a reference plan view showing a transparent portion(transparent electrode);

FIG. 18 is a partly cutaway enlarged sectional view taken long the lineA—A in FIG. 12;

FIG. 19 is a partly cutaway enlarged sectional view taken long the lineB—B in FIG. 12;

FIG. 20 is an enlarged sectional view taken long the line C—C in FIG.12;

FIG. 21 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 22 is a front view showing this example;

FIG. 23 is a back view showing this example;

FIG. 24 is a left (right) side view showing this example;

FIG. 25 is a bottom view showing this example;

FIG. 26 is a reference plan view showing a transparent portion(transparent electrode);

FIG. 27 is a partly cutaway enlarged sectional view taken long the lineA—A in FIG. 21;

FIG. 28 is a partly cutaway enlarged sectional view taken long the lineB—B in FIG. 21;

FIG. 29 is an enlarged sectional view taken long the line C—C in FIG.21;

FIG. 30 is an enlarged sectional view taken long the line D—D in FIG.21;

FIG. 31 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 32 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 33 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 34 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 35 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 36 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 37 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 38 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 39 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 40 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 41 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 42 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 43 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 44 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 45 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 46 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 47 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 48 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 49 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 50 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 51 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 52 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 53 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 54 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 55 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 56 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention;

FIG. 57 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention; and

FIG. 58 is a plan view showing an example of arrangement of electrodesin a light-emitting device according to a further embodiment of theinvention.

In the drawings, the reference numerals 10, 23, 33, 43, 43-1, 53, 63,303 and 301-1 designate light-emitting devices;

6, 16, 26, 36, 46, 56, 66 and 306 designate translucent electrodes;

7 designates a p electrode;

9 designates an n electrode;

17, 27, 37, 47, 57, 81, 91, 101, 111, 121, 131, 141, 151, 161, 171, 181,191, 201, 211, 221, 231, 241 and 251 designate p seat electrodes;

18, 28, 38, 48, 58, 82, 92, 93, 102, 112, 122, 123, 132, 133, 142, 143,152, 166, 172, 182, 192, 193, 202, 212, 222, 223, 233, 2-32, 242, 242,252 designate p auxiliary electrodes;

19, 29, 39, 49, 59, 85, 95, 105, 115, 125, 135, 145, 155, 165, 175, 185,195, 205, 215, 225, 235, 245 and 255 designate n seat electrodes; and

20, 30, 40, 50, 60, 70, 86, 96, 106, 107, 116, 126, 127, 136, 137, 146,156, 166, 176, 186, 196, 216, 226, 227, 236, 237, 246, 247, 248, 256,310 and 320 designate n auxiliary electrodes.

BEST MODE FOR CARRYING OUT THE INVENTION

Respective members constituting the invention will be described below indetail taking a Group III nitride compound semiconductor light-emittingdevice as an example.

An n electrode is formed on an n contact layer revealed by etching asemiconductor layer. Although any material can be selected as thematerial of the n electrode if ohmic contact can be obtained betweenthis material and the p-type Group III nitride compound semiconductor,an aluminum alloy such as a vanadium-aluminum alloy is preferably used.

The shape of then electrode is also optional. According to an aspect ofthe invention, a combination of an n seat electrode and an n auxiliaryelectrode extended from the n seat electrode may be preferably used asthe n electrode so that the distance from any point of a p electrode tothe n electrode is selected to be in a predetermined range. The n seatelectrode may be disposed in substantially the central portion of a sideof the device or may be disposed in a corner portion of the device.Preferably, the n auxiliary electrode has a portion extended from the nseat electrode to the central portion of the device.

It is preferable from the point of view of reduction in the number ofsteps that the n auxiliary electrode is made of the same material by thesame method (same mask) as the n seat electrode. In this case, thethickness of the n auxiliary electrode is selected to be equal to thatof then seat electrode.

The n auxiliary electrode and the n seat electrode may be formedseparately. In this case, the material and thickness of the n auxiliaryelectrode may be selected to be different from those of the n seatelectrode.

The shape of the n seat electrode is not particularly limited if the nseat electrode has an area sufficient to bond electrically conductivewire thereto by a known method.

Since the n auxiliary electrode is formed on a portion where thesemiconductor layer is removed, it is preferable that the width of the nauxiliary electrode is narrowed from the point of view of locallymaximizing the effective area of the semiconductor layer. The width ofthe n auxiliary electrode is preferably selected to be in a range offrom 1 to 40 μm, more preferably in a range of from 2 to 30 μm, furthermore preferably in a range of from 3 to 25 μm, further further morepreferably in a range of from 3 to 20 μm, most preferably in a range offrom 5 to 15 μm.

The material for forming the translucent electrode is not particularlylimited. For example, a Co layer as a first electrode layer and an Aulayer as a second electrode layer are successively laminated from thelower side.

It is preferable that the constituent element of the first electrodelayer is lower in ionization potential than the constituent element ofthe second electrode layer, and that the constituent element of thesecond electrode layer is set as an element better in ohmiccharacteristic to semiconductor than the constituent element of thefirst electrode layer. A heat treatment is also applied to the electrodelayers for forming an alloy with a p-type contact layer. By the heattreatment, the element distribution in the depthwise direction from asurface of the semiconductor becomes a distribution in which theconstituent element of the second electrode layer penetrates more deeplythan the constituent element of the first electrode layer. That is, theelement distribution of the electrode layers is reversed to thedistribution at the time of the formation of the electrode layers. Afterthe formation of the electrode layers, the constituent element of thesecond electrode layer formed on the upper side is migrated to the lowerside whereas the constituent element of the first electrode layer formedon the lower side is migrated to the upper side.

Preferably, the constituent element of the first electrode layer is atleast one element selected from the group consisting of nickel (Ni),cobalt (Co), iron (Fe), copper (Cu), chromium (Cr), tantalum (Ta),vanadium (V), manganese (Mn), aluminum (Al) and silver (Ag). Thethickness of the first electrode layer is selected to be in a range offrom 0.5 to 15 nm. The constituent element of the second electrode layeris at least one element selected from the group consisting of palladium(Pd), gold (Au), iridium (Ir) and platinum (Pt). The thickness of thesecond electrode layer is selected to be in a range of from 3.5 to 25nm. Most preferably, the constituent element of the first electrodelayer is Co and the constituent element of the second electrode layer isAu. In this case, by the heat treatment, the element distribution in thedepthwise direction from the surface of the semiconductor becomes adistribution in which Au penetrates more deeply than Co.

The material for forming the p seat electrode is not particularlylimited too. For example, the p seat electrode is formed as a structurein which a V layer as a first metal layer, an Au layer as a second metallayer and an Al layer as a third metal layer are successively laminatedfrom the lower side.

The element of the first metal layer is selected to be lower inionization potential than that of the second metal layer so that thefirst metal layer can be firmly bonded to a layer under the first metallayer. The element of the second metal layer is selected to be good inbonding characteristic to Al or Au and nonreactive to the translucentelectrode. The element of the third metal layer is preferably selectedto be an element capable of being firmly bonded to a protective film.

Preferably, the constituent element of the first metal layer is at leastone element selected from the group consisting of nickel (Ni), iron(Fe), copper (Cu), chromium (Cr), tantalum (Ta), vanadium (V), manganese(Mn) and cobalt (Co). The thickness of the first metal layer is selectedto be in a range of from 1 to 300 nm.

Preferably, the constituent element of the third metal layer is at leastone element selected from the group consisting of aluminum (Al), nickel(Ni) and titanium (Ti). The thickness of the third metal layer isselected to be in a range of from 1 to 30 nm.

Preferably, the constituent element of the second metal layer is gold(Au). The thickness of the second metal layer is selected to be in arange of from 0.3 to 3 μm.

It is preferable from the point of view of reduction in the number ofsteps that the p auxiliary electrode is made of the same material by thesame method (same mask) as the p seat electrode. In this case, thethickness of the p auxiliary electrode is selected to be equal to thatof the p seat electrode.

The p auxiliary electrode and the p seat electrode may be formedseparately. In this case, the material and thickness of the p auxiliaryelectrode may be selected to be different from those of the p seatelectrode.

The shape of the p seat electrode is not particularly limited if the pseat electrode has an area sufficient to bond electrically conductivewire thereto by a known method. Preferably, the shape of the p seatelectrode different from that of the n seat electrode is used so thatpositions can be confirmed at the time of bonding.

Since the p auxiliary electrode shields light, the width of the pauxiliary electrode is preferably narrowed. The width of the p auxiliaryelectrode is preferably selected to be in a range of from 1 to 40 μm,more preferably in a range of from 2 to 30 μm, further more preferablyin a range of from 3 to 25 μm, further further more preferably in arange of from 3 to 20 μm, most preferably in a range of from 5 to 15 μm.

Preferably, irregularities may be provided around the p seat electrodeand/or the p auxiliary electrode to increase the contact area betweenthe translucent electrode and the p seat electrode and/or between thetranslucent electrode and the p auxiliary electrode.

The circumferential surface of the p seat electrode is preferablyinclined. When the circumferential surface of the seat electrode istapered, a protective film (such as an SiO₂ film) formed on surfaces ofthe seat electrode and the translucent electrode can be also formed onthe tapered portion so that the protective film has the substantiallysame film thickness as designed.

A combination of the p seat electrode and the p auxiliary electrodeextended from the p seat electrode is preferably used so that thedistance from any point of the translucent electrode to the p seatelectrode or the p auxiliary electrode can be selected to be in apredetermined range. The p seat electrode may be disposed insubstantially the central portion of one side of the device or may bedisposed in a corner portion of the device.

Preferably, the p auxiliary electrode is formed like a comb with respectto the n auxiliary electrode. Here, the term “comb” means a state inwhich the p auxiliary electrode and the n auxiliary electrode aredisposed alternately in a plan view of the device.

Preferably, the p auxiliary electrode has a portion disposed in parallelwith the n auxiliary electrode.

Preferably, the heat treatment for alloying the translucent electrodewith the p seat electrode and the p auxiliary electrode is carried outin oxygen-containing gas. In this case, as the oxygen-containing gas, itis possible to use a gas of at least one member or a mixture gasselected from the group consisting of O₂, O₃, CO, CO₂, NO, N₂O, NO₂ andH₂O. Or it is possible to use a mixture gas of an inert gas and at leastone member selected from the group consisting of O₂, O₃, CO, CO₂, NO,N₂O, NO₂ and H₂O. Or it is possible to use a mixture gas of an inert gasand a mixture gas selected from the group consisting of O₂, O₃, CO, CO₂,NO, N₂O, NO₂ and H₂O. In short, the oxygen-containing gas means gas ofoxygen atoms or molecules containing oxygen atoms.

Any atmospheric pressure may be used in the heat treatment if theatmospheric pressure is not smaller than the pressure in which galliumnitride compound semiconductor is not thermally decomposed at the heattreatment temperature. When only O₂ gas is used as the oxygen-containinggas, the oxygen-containing gas may be introduced with pressure of notsmaller than the pressure of decomposition of the gallium nitridecompound semiconductor. When a mixture gas of O₂ gas and another inertgas is used as the oxygen-containing gas, it will be sufficient if thetotal pressure of the mixture gas is made not smaller than the pressureof decomposition of the gallium nitride compound semiconductor and theratio of the amount of the O₂ gas to the total amount of the mixture gasis not smaller than about 10⁻⁶. In short, it will be sufficient if avery small amount of oxygen-containing gas is provided. Incidentally,the upper limit value of the amount of the oxygen-containing gasintroduced is not particularly limited by characteristic of p-typeresistance reduction and electrode alloying. In short, any amount of theoxygen-containing gas introduced may be used if production can be made.

Most preferably, the temperature used in the heat treatment is in arange of from 500 to 600° C. A low-resistance p-type gallium nitridecompound semiconductor with an entirely saturated resistivity can beobtained at a temperature not lower than 500° C. On the other hand, theelectrode can be alloyed well at a temperature not higher than 600° C.The preferred temperature range is from 450 to 650° C.

As for materials for forming the p seat electrode, the p auxiliaryelectrode and the translucent electrode and heat-treating conditionstherefor, refer to Unexamined Japanese Patent Publication No. Hei.9-320984 and Unexamined Japanese Patent Publication No. Hei. 10-209493.

In this description, each of group III nitride compound semiconductorsis represented by the general formula:

Al_(X)Ga_(Y)In_(1-X-Y)N (0≦X≦1, 0≦Y≦1, 0≦X+Y≦1)

which includes so-called binary compounds such as AlN, GaN and InN, andso-called ternary compounds such as Al_(x)Ga_(1-x)N, Al_(x)In_(1-x)N andGa_(x)In_(1-x)N (0<x<1 in the above). The group III elements may bepartially replaced by boron (B), thallium (Tl), or the like. Further,the nitrogen (N) may be partially replaced by phosphorus (P), arsenic(As), antimony (Sb), bismuth (Bi), or the like. The group III nitridecompound semiconductor layer may contain an optional dopant. Si, Ge, Se,Te, C, or the like, can be used as n-type impurities. Mg, Zn, Be, Ca,Sr, Ba, or the like, can be used as p-type impurities. Incidentally,after doped with p-type impurities, the group III nitride compoundsemiconductor may be irradiated with electron beams or plasma or heatedin a furnace. The method of forming each group III nitride compoundsemiconductor layer is not particularly limited. For example, besides ametal organic chemical vapor deposition method (MOCVD method), the groupIII nitride compound semiconductor layer may be formed by a known methodsuch as a molecular beam epitaxy method (MBE method), a halide vaporphase epitaxy method (HVPE method), a sputtering method, an ion-platingmethod, an electron showering method, etc.

Examples of the Group III nitride compound semiconductor device include:optical devices such as a light-emitting diode, a light-receiving diode,a laser diode, a solar cell, etc.; bipolar devices such as a rectifier,a thyristor, a transistor, etc.; unipolar devices such as an FET, etc.;and electronic devices such as a microwave device, etc. The presentinvention may be applied also to laminates which are intermediates ofthese devices.

Incidentally, a homo structure, a hetero structure or a double heterostructure provided with an MIS junction, a PIN junction or a p-njunction can be used as the structure of the light-emitting device. Aquantum well structure (single quantum well structure or multiplequantum well structure) may be used as the light-emitting layer.

<Embodiments>

An embodiment of the invention will be described below.

This embodiment shows a light-emitting diode 10. FIG. 1 shows theconfiguration thereof. Incidentally, FIG. 1 is a view not for exactlyreflecting the thickness and width proportion of respective layers butfor explaining the configuration of the layers.

Layer Composition Dopant (Thickness) Protective layer 14 SiO₂  (0.3 μm)Au (6 nm)/Co Translucent electrode 6 (1.5 nm) p-type clad layer 5 p-GaNMg  (0.3 μm) Light-emitting layer 4 Superlattice structure Quantum welllayer In_(0.15)Ga_(0.85)N  (3.5 nm) Barrier layer GaN  (3.5 nm) Thenumber of repeated quantum well and barrier layers: 1 to 10 n-type cladlayer 3 n-GaN Si  (4 μm) AlN buffer layer 2 AlN  (60 nm) Substrate 1Sapphire (300 μm) (surface a)

The n-type clad layer 3 may be of a double-layered structure having ann− layer of low electron density on the light-emitting layer 4 side andan n+ layer of high electron density on the buffer layer 2 side. Thelatter is called n-type contact layer.

The light-emitting layer 4 is not limited to the superlattice structure.A single hetero type structure, a double hetero type structure, a homojunction type structure, or the like, may be used as the structure ofthe light-emitting device.

A group III nitride compound semiconductor layer doped with an acceptorsuch as magnesium and having a wide band gap may be interposed betweenthe light-emitting layer 4 and the p-type clad layer 5. This is providedfor preventing electrons injected into the light-emitting layer 4 fromdispersing into the p-type clad layer 5.

The p-type clad layer 5 may be of a double-layered structure having a p−layer of low hole density on the light-emitting layer 4 side and a p+layer of high hole density on the electrode side. The latter is calledp-type contact layer.

In the light-emitting diode configured as described above, each of thegroup III nitride compound semiconductor layers is formed by executionof MOCVD under a general condition.

Then, a mask is formed and the p-type clad layer 5, the active layer 4and the n-type clad layer 3 are partially removed by reactive ionetching to thereby reveal an n electrode-forming surface 11 on which ann electrode 9 will be formed.

A Co layer (1.5 nm) and an Au layer (60 nm) are successively laminatedonto the whole surface of a wafer by an evaporation system. Next, aphoto resist is applied thereon evenly and then removed from the nelectrode-forming surface 11 and a portion (clearance region 13) about10 μm wide from its circumference by photolithography. The translucentelectrode-forming material is removed from this portion by etching tothereby reveal the semiconductor layer. Then, the photo resist isremoved.

Then, a V layer (17.5 nm), an Au layer (1.5 μm) and an Al layer (10 nm)are successively deposited and laminated by a lift-off method to therebyform a p seat electrode 7 and a p auxiliary electrode 7 (p electrode 7).

An n electrode 9 made of vanadium and aluminum is also formed by alift-off method.

The sample obtained in the aforementioned manner is put into a heatingfurnace. The inside of the furnace is evacuated to be not higher than 1Pa. Then, O₂ is fed to the furnace so that the degree of vacuum reachesten and several Pa. In this condition, the temperature of the furnace isset at 550° C. and heating is performed for about 4 minutes. Thus, thematerial of the translucent electrode 6 and the materials of the p seatelectrode and the p auxiliary electrode are alloyed and connected toeach other to thereby form a p electrode.

According to the inventors' examination, there is little electriccurrent injected into the p-type clad layer just under the p seatelectrode and the p auxiliary electrode. It is anticipated that contactresistance is relatively high just under the p seat electrode and the pauxiliary electrode because the aforementioned inversion of thedistribution does not occur in the Au/Co deposited layers constitutingthe translucent electrode. Hence, the interface between thecircumferential surface of the p seat/auxiliary electrode and thetranslucent electrode 6 becomes an electrical connection surfaceeffective to the two. That is, the electric current applied to the pseat electrode flows into the translucent electrode through thecircumferential surface of the p seat/auxiliary electrode and diffusesinto the whole surface of the translucent electrode, so that the currentis injected into the whole surface of the p-type semiconductor layerevenly.

The substantially whole surface except a region provided on the p seatelectrode to be subjected to wire bonding or the like and the uppersurface and circumferential edge portion of the n electrode is coveredwith an electrically insulating translucent protective film 14 (siliconoxide, silicon nitride, titanium oxide, aluminum oxide, or the like). Asputtering method or a CVD method can be used as a method for formingthe protective film 14.

An example of arrangement of electrodes in the light-emitting device 10obtained in the aforementioned manner is shown in FIGS. 2 to 11. In FIG.2, the reference numeral 16 designates a translucent electrode; 17, a pseat electrode; and 18, a p auxiliary electrode. The p auxiliaryelectrode 18 is formed so as to be integrated with the p seat electrode17. The p seat electrode 17 is disposed in the center of a side so thatthe p auxiliary electrode 18 is shaped like an E figure opened upwardwith the p seat electrode 17 as its center. The reference numeral 15designates a parting line for the protective film.

An n seat electrode 19 is formed in substantially the center of a sideopposite to the p seat electrode 17. An n auxiliary electrode 20 isformed so as to be integrated with the n seat electrode 19. The nauxiliary electrode 20 is shaped like a U figure opened downward withthe n seat electrode as its center. The n auxiliary electrode 20 isdisposed so as to be parallel with the p auxiliary electrode 18 andshaped like a comb.

The reference numeral 21 designates an n electrode-forming surface; and22, a substrate material surface which is revealed for dicing. Theprotective film 24 is a portion hatched in FIG. 7.

The device is a square having a length of 1000 μm on each side.

An example of arrangement of electrodes in another light-emitting device23 is shown in FIGS. 12 to 20. In FIG. 12, the reference numeral 26designates a translucent electrode; 27, a p seat electrode; and 28, a pauxiliary electrode. The p auxiliary electrode 28 is formed so as to beintegrated with the p seat electrode 27. The p seat electrode 27 isdisposed in the center of a side so that the p auxiliary electrode 28 isshaped like a U figure opened upward with the p seat electrode 27 as itscenter. The reference numeral 25 designates a parting line for theprotective film.

An n seat electrode 29 is formed in substantially the center of a sideopposite to the p seat electrode 27. An n auxiliary electrode 30 isformed so as to be integrated with the n seat electrode 29. The nauxiliary electrode 30 is extended from the n seat electrode toward thep seat electrode 27.

The reference numeral 31 designates an n electrode-forming surface; and32, a substrate material surface which is revealed for dicing. Theprotective film 34 is a portion hatched in FIG. 17.

The device is a square having a length of 600 μm on each side.

An example of arrangement of electrodes in a further light-emittingdevice 33 is shown in FIGS. 21 to 30. In FIG. 21, the reference numeral36 designates a translucent electrode; 37, p seat electrodes; and 38, ap auxiliary electrode. The p auxiliary electrode 38 is formed so as tobe integrated with the p seat electrodes 37. The p seat electrodes 37are disposed at opposite ends of a side so that the p auxiliaryelectrode 38 is shaped like an E figure opened upward. The referencenumeral 35 designates a parting line for the protective film.

N seat electrodes 39 are formed on a side opposite to the p seatelectrodes 37. An n auxiliary electrode 40 is formed so as to beintegrated with the n seat electrodes 39. The n auxiliary electrode 40is shaped like a U figure opened downward. The n seat electrodes 39 aredisposed in base portions of the n auxiliary electrode 40. The nauxiliary electrode 40 is disposed so as to be parallel with the pauxiliary electrode 38 and shaped like a comb.

The reference numeral 41 designates an n electrode-forming surface; and42, a substrate material surface which is revealed for dicing. Theprotective film 34 is a portion hatched in FIG. 26.

The device is a square having a length of 1000 μm on each side.

An example of arrangement of electrodes in a further light-emittingdevice 43 is shown in FIG. 31. In FIG. 31, the reference numeral 46designates a translucent electrode; 47, p seat electrodes; and 48, a pauxiliary electrode. The p auxiliary electrode 48 is formed so as to beintegrated with the p seat electrodes 47. The p seat electrodes 47 aredisposed in opposite corner portions. The p auxiliary electrode 48 isformed to be extended from the p seat electrodes 47 and 47 along upperand left sides of the device in the drawing. The reference numeral 45designates a parting line for the protective film.

An n seat electrode 49 is formed in a corner portion of the device. An nauxiliary electrode 50 is formed so as to be integrated with the n seatelectrode 49. The n auxiliary electrode 50 is formed in a range of fromthe n seat electrode 49 to the central portion of the device so as to beextended to a neighbor of an opposite corner portion.

The reference numeral 51 designates an n electrode-forming surface; and52, a substrate material surface which is revealed for dicing.

The device is a square having a length of 800 μm on each side.

FIG. 32 shows a modification of FIG. 31. In the device 43-1 of FIG. 32,the n auxiliary electrode 50-1 has branches 50-2 and 50-3. The branches50-2 and 50-3 are extended toward the p seat electrodes 47 and 47respectively.

In FIG. 32, parts the same as those in FIG. 31 are referred to bynumerals the same as those in FIG. 31 for the sake of omission ofdescription thereof.

An example of arrangement of electrodes in a further light-emittingdevice 53 is shown in FIG. 33. In FIG. 33, the reference numeral 56designates translucent electrodes; 57, p seat electrodes; and 58, pauxiliary electrodes. The p auxiliary electrodes 58 are formed so as tobe integrated with the p seat electrodes 57 respectively. The p seatelectrodes 57 are disposed in opposite corner portions. The p auxiliaryelectrodes 58 are formed to be extended from the p seat electrodes 47and 47 along upper and left sides of the device in the drawing. Thereference numeral 55 designates a parting line for the protective film.

An n seat electrode 59 is formed in the central portion of the device.An n auxiliary electrode 60 is formed so as to be integrated with the nseat electrode 59. The n auxiliary electrode 60 is formed in parallelwith the p auxiliary electrode 58 from the n seat electrode 59 so as tobe extended to a neighbor of the edge of the device.

The reference numeral 61 designates an n electrode-forming surface; and62, a substrate material surface which is revealed for dicing.

The device is a square having a length of 800 μm on each side.

An example of arrangement of electrodes in a further light-emittingdevice 63 is shown in FIG. 34. In FIG. 34, the reference numeral 66designates translucent electrodes; and 67, p seat electrodes. In thisexample, the p auxiliary electrode is omitted. The p seat electrodes 67are disposed in opposite corner portions. The reference numeral 55designates a parting line for the protective film.

An n seat electrode 69 is formed in the central portion of the device.An n auxiliary electrode 70 is formed so as to be integrated with the nseat electrode 69. The n auxiliary electrode 70 is extended from the nseat electrode 69 to corner portions of the device in which there is nop seat electrode.

The reference numeral 71 designates an n electrode-forming surface; and72, a substrate material surface which is revealed for dicing.

The device is a square having a length of 800 μm on each side.

Other examples of arrangement of electrodes in a light-emitting deviceare shown in FIGS. 35 to 52. In these examples of these drawings, only pelectrodes and n electrodes (hatched) are shown for the sake ofsimplification of description. Also in each of the examples shown inFIGS. 35 to 52, a p electrode or p electrodes are formed on atranslucent electrode or translucent electrodes which is or are stuckonto the substantially whole surface of the p-type semiconductor layer,as described in each of the examples shown in FIG. 34 and the drawingsbefore FIG. 34. The n electrode-forming surface and the protective filmare not shown in the drawings but are formed in the same manner as inthe previous examples. In the following description, positionalrelations (upper, lower, left and right) of parts are defined on thebasis of the drawings only for the sake of convenience of description.

In each of these examples, the length of one side of the light-emittingdevice is not smaller than 500 μm.

In the example of FIG. 35, p seat electrodes 81 and 81 are formed inopposite corner portions of the device. P auxiliary electrodes 82 and 82are formed so as to be extended from the p seat electrodes 81 and 81along respective sides. N seat electrodes 85 and 85 are formed inresidual opposite corner portions of the device. N auxiliary electrodes86 and 86 are formed so as to be extended from the n seat electrodes 85and 85 along upper and lower sides respectively.

In the example of FIG. 36, a p seat electrode 91 is formed in one cornerportion of the device. A first p auxiliary electrode 92 is formed so asto be extended from the p seat electrode 91 along left and lower sidesof the device. A second p auxiliary electrode 93 is formed so as to beextended from the p seat electrode 91 along an upper side of the device.An n seat electrode 95 is disposed in the substantially central portionof a right side. An n auxiliary electrode 96 is provided so as to beextended from the n seat electrode 95 to the central portion of thedevice.

In the example of FIG. 37, p seat electrodes 101 and 101 are formed intwo upper corner portions of the device. P auxiliary electrodes 102 and102 each bent so as to be L-shaped are extended from the p seatelectrodes 101 and 101 respectively. N seat electrodes 105 are formed intwo lower corner portions respectively. First auxiliary electrodes 106and 106 are extended upward from the n seat electrodes 105 along leftand right sides respectively. A second auxiliary electrode 107 is shapedlike a reverse T figure, that is, is extended from a lower side to anupper side through the center of the device. The portion extended upwardfrom the center of the lower side is parallel with the p auxiliaryelectrodes 102 and 102.

In the example of FIG. 38, a p seat electrode 111 is formed in thecentral portion of the device. P auxiliary electrodes 112 and 112 areextended on one diagonal line from the p seat electrode 111. N seatelectrodes 115 and 115 are formed in opposite corner portions of thedevice. N auxiliary electrodes 116 and 116 are formed alongcircumferential sides of the device so that the two n seat electrodes115 and 115 are connected to each other by the n auxiliary electrodes116 and 116.

In the example of FIG. 39, a p seat electrode 121 is provided slightlybelow the center of a left side. A first p auxiliary electrode 122 isextended downward along the left side from the p seat electrode 121 andfurther extended along a lower side. A second p auxiliary electrode 123is extended from the lower left corner at an included angle of about 30degrees with respect to the lower side. An n seat electrode 125 isprovided slightly above the center of a right side. A first n auxiliaryelectrode 126 is extended upward along the right side from the n seatelectrode 125 and further extended along an upper side. A second pauxiliary electrode 127 is extended from the upper right corner at anincluded angle of about 30 degrees with respect to the upper side.

In the example of FIG. 40, a p seat electrode 131 is formed insubstantially the center of a left side. A first p auxiliary electrode132 is extended upward along the left side from the p seat electrode 131and further extended along an upper side. A second p auxiliary electrode133 is extended downward perpendicularly from portion on a slightlyright-hand side of the upper side center. An n seat electrode 135 isformed in substantially the center of a right side. A first n auxiliaryelectrode 136 is extended downward along the right side from the n seatelectrode 135 and further extended along a lower side. A second nauxiliary electrode 137 is extended upward perpendicularly from aportion on a slightly left-hand side of the lower side center.

In the example of FIG. 41, a p seat electrode 141 is formed in a lowerleft corner. A first p auxiliary electrode 142 is extended on a diagonalline from the p seat electrode 141. Second p auxiliary electrodes 143and 143 are extended perpendicularly from the first p auxiliaryelectrode 142 in the central portion of the device. An n seat electrode145 is formed in an upper right corner of the device. First n auxiliaryelectrodes 146 and 146 are extended from the n seat electrode 145 alongupper and right sides respectively.

In the example of FIG. 42, a p seat electrode 151 is formed in a lowerleft corner of the device. A first p auxiliary electrode 152 is extendedupward along a left side from the p seat electrode 151 and furtherextended along an upper side and extended perpendicularly downward froma portion on a slightly right-hand side of the upper side center. An nseat electrode 155 is formed in an upper right corner of the device. Afirst n auxiliary electrode 156 is extended downward along a right sidefrom the n seat electrode 155 and further extended along a lower sideand extended perpendicularly downward from a portion on a slightlyleft-hand side of the lower side center.

In the example of FIG. 43, a p seat electrode 161 is formed in an upperleft corner of the device. A first p auxiliary electrode 162 is extendedalong the whole of upper, right and left sides. An n seat electrode 165is formed in substantially the center of the device. First n auxiliaryelectrodes 166, 166, 166 and 166 are extended on diagonal lines from then seat electrode 165.

In the example of FIG. 44, a p seat electrode 171 is formed in an upperleft corner of the device. P auxiliary electrodes 172 and 172 areextended along upper and left sides respectively from the p seatelectrode 171. An n seat electrode 175 is formed in a lower right cornerof the device. From then seat electrode 175, first n auxiliaryelectrodes 176 and 176 are extended along right and lower sidesrespectively, and a second n auxiliary electrode 177 is further extendedon a diagonal line.

In the example of FIG. 45, p seat electrodes 181 and 181 are formedrespectively in a lower left corner and an upper right corner of thedevice. First p auxiliary electrodes 182, 182, 182 and 182 are extendedalong respective sides from the p seat electrodes 181 and 181. N seatelectrodes 185 and 185 are formed respectively in a lower right cornerand an upper left corner of the device. A first n auxiliary electrode186 is formed so as to connect the n seat electrodes 185 and 185 to eachother.

In the example of FIG. 46, p seat electrodes 191 and 191 are formed atopposite ends of an upper side. A first p auxiliary electrode 192 isformed along the upper side so as to connect the p seat electrodes 191and 191 to each other. A second p auxiliary electrode 193 is extendedperpendicularly downward from the center of the first p auxiliaryelectrode 192. N seat electrodes 195 and 195 are formed at opposite endsof a lower side. First n auxiliary electrodes 196 and 196 are extendedupward along left and right sides from the n seat electrodes 195 and 195respectively.

In the example of FIG. 47, a p seat electrode 201 is formed in an upperleft corner of the device. A first p auxiliary electrode is extendedfrom the p seat electrode 201 and formed along the whole circumferentialportion. An n seat electrode 205 is formed in substantially the centerof the device.

In the example of FIG. 48, p seat electrodes 211 and 211 are formedrespectively in a lower left corner and an upper right corner of thedevice. First p auxiliary electrodes 212, 212, 212 and 212 are extendedalong respective sides from the p seat electrodes 211 and 211. An n seatelectrode 215 is formed in substantially the center of the device. Firstn auxiliary electrodes 216 and 216 are extended from the n seatelectrode 215 on a diagonal line containing no p seat electrode.

In the example of FIG. 49, a p seat electrode 221 is formed in an upperleft corner of the device. From the p seat electrode 221, a first pauxiliary electrode 222 is extended along a left side, and a second pauxiliary electrode 223 is extended along an upper side and furtherextended perpendicularly downward from a portion on a slightlyright-hand side of the upper side center. An n seat electrode 225 isformed in a lower right corner of the device. From the n seat electrode225, a first n auxiliary electrode 226 is extended along a right side,and a second n auxiliary electrode 227 is extended along a lower sideand further extended perpendicularly upward from a portion on a slightlyleft-hand side of the lower side center.

In the example of FIG. 50, a p seat electrode 231 is formed insubstantially the center of a lower side. A first p auxiliary electrode232 is extended rightward along the lower side from the p seat electrode231 and further extended upward along a right side. Further, a second pauxiliary electrode 233 is extended slightly leftward from the p seatelectrode 231 and further extended perpendicularly upward therefrom. Ann seat electrode 235 is formed in substantially the center of a lowerside. A first n auxiliary electrode 236 is extended leftward along theupper side from the n seat electrode 235 and further extended downwardalong a left side. Further, a second n auxiliary electrode 237 isextended slightly rightward from the n seat electrode 235 and furtherextended perpendicularly downward therefrom.

In the example of FIG. 51, the device is a rectangle in plan view. A pseat electrode 241 is formed on a slightly left-hand side of a lowerside center. A first p auxiliary electrode 242 is extended rightwardalong the lower side from the p seat electrode 241 and further extendedupward along a right side. Further, a second p auxiliary electrode 243is extended slightly leftward from the p seat electrode 241 and furtherextended perpendicularly upward therefrom. An n seat electrode 245 isformed on a slightly right-hand side of an upper side center. A first nauxiliary electrode 246 is extended leftward along the upper side fromthe n seat electrode 245 and further extended downward along a leftside. A second n auxiliary electrode 247 is extended perpendicularlydownward from the first auxiliary electrode 246. A third n auxiliaryelectrode 248 is extended slightly rightward from the n seat electrode245 and further extended perpendicularly downward.

In the example of FIG. 52, a p seat electrode 251 is formed in a lowerright corner of the device. First p auxiliary electrodes 252 and 252 areextended slightly along right and lower sides respectively and furtherextended both upward and leftward in parallel with a diagonal line. An nseat electrode 255 is formed in an upper left corner of the device.First n auxiliary electrodes 256 and 256 are extended from the n seatelectrode 255 and formed along an upper side and a left siderespectively. Further, a second n auxiliary electrode 257 is extended ona diagonal line from the n seat electrode 255, so that the second nauxiliary electrode 257 is disposed in parallel with the p auxiliaryelectrodes so as to be shaped like a comb.

An example of arrangement of electrodes in a further light-emittingdevice 303 is shown in FIG. 53. In FIG. 53, the reference numeral 306designates a translucent electrode; 307, a p seat electrode; and 308, ap auxiliary electrode. The p auxiliary electrode 308 is formed so as tobe integrated with the p seat electrode 307. The p seat electrode 307 isdisposed in substantially the center of a lower side as shown in thedrawing. The p auxiliary electrode 308 is extended from opposite sidesof the p seat electrode 307 and formed along a lower side.

An n seat electrode 309 is formed in substantially the center of anupper side. An n auxiliary electrode 310 is formed so as to beintegrated with the n seat electrode 309. The n auxiliary electrode 310is extended from the n seat electrode 309 so as to be shaped like a Cfigure opened toward the central portion of the device. An openingportion of the n auxiliary electrode 310 is opposite to the p seatelectrode 307.

The reference numeral 311 designates an n electrode-forming surface; and312, a substrate material surface which is revealed for dicing.

The device is a square having a length of 1000 μm on each side.

FIG. 54 shows a modification of FIG. 53. An n auxiliary electrode 320shaped like a C figure deformed compared with the C figure shown in FIG.53 is used in the device 303-1 of FIG. 54. The reference numeral 321designates an n electrode-forming surface.

In FIG. 54, parts the same as those in FIG. 53 are referred to bynumerals the same as those in FIG. 53 for the sake of omission ofdescription thereof.

An example of arrangement of electrodes in a further light-emittingdevice 323 is shown in FIG. 55. In FIG. 55, parts the same as those inFIG. 53 are referred to by numerals the same as those in FIG. 53 for thesake of omission of description thereof. In the light-emitting device323, a second p auxiliary electrode 325 is disposed in substantially thecenter, and third and fourth auxiliary electrodes 326 and 327 are formedin corner portions opposite to the first auxiliary electrode 308. Thesecond, third and third auxiliary electrodes 325, 326 and 327 areseparated from the p seat electrode 307. The electric potential of eachof the second, third and fourth auxiliary electrodes 325, 326 and 327 isdefined by the electric potential of a portion nearest to the p seatelectrode 307 and the first p auxiliary electrode 308, so that the wholeregion of each of the second, third and fourth auxiliary electrodes 325,326 and 327 has the same electric potential. Hence, the same electricpotential region given by the second p auxiliary electrode 325 exists atsubstantially equal distances from the inner side of the C-shaped nauxiliary electrode 310. The electric current distribution in the nauxiliary electrode 310 is made more uniform. Further, with respect tothe third and fourth p auxiliary electrodes 326 and 327, the electricpotentials at lower ends (portions nearest to the first p auxiliaryelectrode 308) of the third and fourth p auxiliary electrodes 326 and327 are given to a counter side (upper side in the drawing) locatedfarthest from the p seat electrode 307 and the first p auxiliaryelectrode 308. Hence, the electric current distribution in the upperside can be improved.

The device is a square having a length of 1000 μm on each side.

An example of arrangement of electrodes in a further light-emittingdevice 333 is shown in FIG. 56. In FIG. 56, parts the same as those inFIG. 53 are referred to by numerals the same as those in FIG. 53 for thesake of omission of description thereof. In the light-emitting device333, a second p seat electrode 336 and a third p seat electrode 337 areformed respectively in opposite ends of an upper side (the side oppositeto the first p seat electrode 307). When die-bonding is applied to thesecond and third p seat electrodes 336 and 337, the electric potentialsof the first, second and third p seat electrodes 307, 336 and 337 isequalized to one another. Hence, there can be obtained electric currentdensity uniform on the substantially whole surface of the light-emittingdevice 333.

The device is a square having a length of 1000 μm on each side.

An example of arrangement of electrodes in a further light-emittingdevice 343 is shown in FIG. 57. In FIG. 57, the reference numeral 346designates a translucent electrode; 347, a first p seat electrode; and348 and 349, p auxiliary electrodes formed so as to be integrated withthe first p seat electrode 347. The first p seat electrode 347 is formedin one corner of the light-emitting device 343. The p auxiliaryelectrode 348 is extended along a lower side to a position about ⅔ aslarge as the lower side. The p auxiliary electrode 349 is extended alonga right side to a position about ⅔ as large as the right side. A secondp seat electrode 357 is formed in a corner portion opposite to the firstp seat electrode 347. A p auxiliary electrode 358 is formed so as to beintegrated with the second p seat electrode 357, and is extended alongan upper side to a position about ⅔ as large as the upper side. A pauxiliary electrode 359 is further formed so as to be integrated withthe second p seat electrode 357, and is extended along a left side to aposition about ⅔ as large as the left side.

An n seat electrode 349 is formed in substantially the center.

The reference numeral 351 designates an n electrode-forming surface; and352, a substrate material surface which is revealed for dicing.

An example of arrangement of electrodes in a further light-emittingdevice 363 is shown in FIG. 58. In FIG. 57, parts the same as those inFIG. 56 are referred to by numerals the same as those in FIG. 56 for thesake of omission of description thereof. The reference numeral 367designates a first p seat electrode; and 368, a p auxiliary electrodeformed so as to be integrated with the first p seat electrode 367. Thefirst p seat electrode 367 is formed in one corner of the light-emittingdevice 363. The p auxiliary electrode 368 is extended from a lower sideto a left side so as to reach a position about a half as large as theleft side. A second p seat electrode 377 is formed in a corner portionopposite to the first p seat electrode 367. A p auxiliary electrode 378is formed so as to be integrated with the second p seat electrode 377,and is extended from an upper side to a right side so as to reach aposition about a half as large as the right side.

INDUSTRIAL APPLICABILITY

The invention is not limited to the description on the mode for carryingout the invention and the embodiments at all. Various modificationswhich can be easily conceived by those skilled in the art may becontained in the invention without departing from the description ofclaims.

The following paragraphs are disclosed.

11. A Group III nitride compound semiconductor device characterized inthat an n auxiliary electrode is extended from an n seat electrode to acentral portion of the device in a plan view of the device.

12. A Group III nitride compound semiconductor device according to theparagraph 11, characterized in that the device is a rectangle in planview, and has a length of not smaller than 500 μm on one side.

13. A Group III nitride compound semiconductor device according to theparagraph 11 or 12, characterized in that the device has a translucentelectrode, and a p electrode constituted by a p seat electrode and a pauxiliary electrode extended from the p seat electrode.

14. A Group III nitride compound semiconductor device according to theparagraph 13, characterized in that the distance from any point of thetranslucent electrode to either of the p seat electrode and the pauxiliary electrode is in a range of from 0 to 1000 μm.

15. A Group III nitride compound semiconductor according to theparagraph 13 or 14, characterized in that the n auxiliary electrode andthe p auxiliary electrode are arranged like a comb.

16. A Group III nitride compound semiconductor device according to anyone of the paragraphs 13 through 15, characterized in that the nauxiliary electrode and the p auxiliary electrode include portionsarranged in parallel with each other.

17. A Group ITT nitride compound semiconductor device according to anyone of the paragraphs 13 through 16, characterized in that a pluralityof n seat electrodes as described above and a plurality of p seatelectrodes as described above are arranged.

18. A Group III nitride compound semiconductor device according to anyone of the paragraphs 11 through 17, characterized by having either alight-emitting device structure or a light-receiving device structure.

21. A Group III nitride compound semiconductor device characterized inthat the distance from any point of a translucent electrode to either ap seat electrode or a p auxiliary electrode is in a range of from 0 to1000 μm.

22. A Group III nitride compound semiconductor device according to theparagraph 21, characterized in that the device is a rectangle in planview, and has a length of not smaller than 500 μm on one side.

23. A Group III nitride compound semiconductor according to theparagraph 21 or 22, characterized in that the n auxiliary electrode andthe p auxiliary electrode are arranged like a comb.

24. A Group III nitride compound semiconductor device according to anyone of the paragraphs 21 through 23, characterized in that the nauxiliary electrode and the p auxiliary electrode include portionsarranged in parallel with each other.

25. A Group III nitride compound semiconductor device according to anyone of the paragraphs 21 through 24, characterized in that a pluralityof n seat electrodes as described above and a plurality of p seatelectrodes as described above are arranged.

26. A Group III nitride compound semiconductor device according to anyone of the paragraphs 21 through 25, characterized by having either alight-emitting device structure or a light-receiving device structure.

31. A Group III nitride compound semiconductor having:

an n electrode having an n seat electrode, and an n auxiliary electrode;

a translucent electrode; and

a p electrode having a p seat electrode, and a p auxiliary electrode,

the device characterized in that then auxiliary electrode and the pauxiliary electrode are arranged like a comb in a plan view of thedevice.

32. A Group III nitride compound semiconductor device according to theparagraph 31, characterized in that the device is a rectangle in planview, and has a length of not smaller than 500 μm on one side.

33. A Group III nitride compound semiconductor device according to theparagraph 31 or 32, characterized in that a plurality of n seatelectrodes as described above and a plurality of p seat electrodes asdescribed above are arranged.

34. A Group III nitride compound semiconductor device according to anyone of the paragraphs 31 through 33, characterized by having either alight-emitting device structure or a light-receiving device structure.

41. A Group III nitride compound semiconductor having:

an n electrode having an n seat electrode, and an n auxiliary electrode;

a translucent electrode; and

a p electrode having a p seat electrode, and a p auxiliary electrode,

the device characterized in that then auxiliary electrode and the pauxiliary electrode include portions arranged in parallel with eachother in a plan view of the device.

42. A Group III nitride compound semiconductor device according to theparagraph 41, characterized in that the device is a rectangle in planview, and has a length of not smaller than 500 μm on one side.

43. A Group III nitride compound semiconductor device according to theparagraph 41 or 42, characterized in that a plurality of n seatelectrodes as described above and a plurality of p seat electrodes asdescribed above are arranged.

44. A Group III nitride compound semiconductor device according to anyone of the paragraphs 41 through 43, characterized by having either alight-emitting device structure or a light-receiving device structure.

51. A Group III nitride compound semiconductor device characterized inthat: the device is a rectangle in plan view, and has a length of notsmaller than 500 μm on one side; and the device has a plurality of nseat electrodes, and a plurality of p seat electrodes.

52. A Group III nitride compound semiconductor device according to theparagraph 51, characterized in that: two n seat electrodes are disposedon a first side whereas two p seat electrodes are disposed on a secondside opposite to the first side; and n auxiliary electrodes are extendedfrom the n seat electrodes whereas p auxiliary electrodes are extendedfrom the p seat electrodes.

53. A Group III nitride compound semiconductor device according to theparagraph 51 or 52, characterized by having either a light-emittingdevice structure or a light-receiving device structure.

What is claimed is:
 1. A Group III nitride compound semiconductor device, comprising: an n electrode; and a p electrode, wherein an outermost diameter of said Group III nitride compound semiconductor device is not smaller than 700 μm, and a distance from said n electrode to a farthest point of said p electrode is not larger than 500 μm.
 2. A Group III nitride compound semiconductor device according to claim 1, wherein said device is a rectangle in plan view, and has a length of not smaller than 500 μm on one side.
 3. A Group III nitride compound semiconductor device according to claim 1, wherein said n electrode includes an n seat electrode and an n auxiliary electrode, which extends from said n seat electrode, and at least one part of said n auxiliary electrode extends to a central portion of said device in a plan view of said device.
 4. A Group III nitride compound semiconductor device according to claim 1, wherein said p electrode includes a p seat electrode and a p auxiliary electrode, which extends from said p seat electrode.
 5. A Group III nitride compound semiconductor device according to claim 4, wherein said devices further comprises: a translucent electrode on which said p electrode is provided, wherein a distance between any point of said translucent electrode and either said p seat electrode or said p auxiliary electrode is in a range of from 0 to 1000 μm.
 6. A Group III nitride compound semiconductor according to claim 4, wherein said n electrode includes an n seat electrode and an n auxiliary electrode, which extends from said n seat electrode, and said n auxiliary electrode and said p auxiliary electrode are arranged like a comb.
 7. A Group III nitride compound semiconductor device according to claim 6, wherein said n seat electrode comprises a plurality of n seat electrodes and said p seat electrode comprises a plurality of p seat electrodes.
 8. A Group III nitride compound semiconductor device according to claim 4, wherein said n electrode includes an n seat electrode and an n auxiliary electrode, which extends from said n seat electrode, and said n auxiliary electrode and said p auxiliary electrode include portions disposed in parallel with each other.
 9. A Group III nitride compound semiconductor device according to claim 8, wherein said n seat electrode comprises a plurality of n seat electrodes and said p seat electrode comprises a plurality of p seat electrodes.
 10. A Group III nitride compound semiconductor device according to claim 1, including a light-emitting device structure or a light-receiving device structure.
 11. A Group III nitride compound semiconductor device, comprising: an n electrode; and a p electrode, wherein an outermost diameter of said Group III nitride compound semiconductor device is not smaller than 700 μm, and a distance X μm from any point on said p electrode to said n electrode satisfies the requirement: X=t/ñ,  in which t is a thickness of an n-type semiconductor layer and ñ is a resistivity of the n-type semiconductor layer.
 12. A Group III nitride compound semiconductor device, comprising: an n electrode; an n-type semiconductor layer with a resistivity of from 0.004 to 0.01 Ω·m and a thickness of from 3 to 5 μm; and a p electrode, wherein an outermost diameter of said Group III nitride compound semiconductor device is not smaller than 700 μm, and a distance from said n electrode to a farthest point of said p electrode is in a range of from 300 to 500 μm. 